Electric motors, such as that of an electric blower motor mounted onto a heating, ventilating, and air-conditioning (HVAC) module of a vehicle, often produce vibrations in operation. The vibration can be transmitted from the motor through the HVAC module to other components of the HVAC system and eventually to the passenger compartment of a vehicle. To isolate the motor vibrations, the electric motor is typically fastened onto a motor mount assembly that has vibration isolating features, which is in turn mounted to the HVAC module. The motor mount assembly can be a separate component or an integral part of the HVAC module.
General attaching arrangements used to fasten an electric motor to an vibration isolating motor mount assembly and other known electric motor mount assemblies have included the use of axial mounting studs protruding from the motor housing; band type mounts in the form of hoops or ring shaped wire straps that encircle the frame of the motor and attach to the motor mount by mounting arms; and bases that cradle the motors, where the bases have mount points to attach to the motor mount assembly.
U.S. patent application Ser. No. 11/542,542, assigned to Delphi Technologies Inc. on Oct. 3, 2006, discloses an electric blower motor mount assembly for a HVAC module having specially designed plastic isolation posts for isolating vibrations from the motor. The plastic isolation posts extend axially relative to the motor housing. One end of the post is attached to a support structure extending from the motor housing and the other end may be integrally molded with the HVAC module. The isolation posts are designed to provide a desired torsional stiffness to target the natural frequency of the motor and mount system such that isolation/attenuation occurs in the commutation order frequency range. In addition, the posts are designed to provide adequate radial stiffness such that the radial resonant frequency is not shifted in the 1st order range (e.g. 16-67 Hz).
The use of known attaching arrangements to attach an electric motor to a motor mount assembly requires an inventory of fasteners and increases the complexity of assembly. Several traditional methods of attachment may be used to attach the motor to the plastic isolation posts as taught by '542; however, there are shortcomings to such traditional methods. Use of screws would require a significant increase in the diameter of the plastic posts and would negatively impact their stiffness as well as adding labor costs and quality problems. Use of push nuts and Tinnerman nuts have similar problems of adding module assembly labor hours, as well as the potential for quality problems associated with dropped fasteners lodging in the motor or module. Snap fits require an undercut in the posts which adds molding complexity. Also, snap fits generally have some “slop” which would allow excessive motor vibration. Attachment methods such as heat staking add capital cost and require extra radial clearance for the tooling to access the plastic nub for melting.
What is needed and desired is a high quality, cost effective, reliable, and compact motor attachment assembly to attach an electric motor to plastic isolation posts without significantly affecting the diameter of the plastic posts, without negatively affecting the designed isolation properties of the plastic posts, and without the potential of dropping fasteners into the final assembly.